This invention relates to a binding element for binding a stack of documents comprised of loose sheets, having a spine piece and two side pieces, the side pieces being arranged essentially perpendicular to the spine piece.
It is an object of the present invention to provide a low-cost and easy-to-use binding element.
This object is accomplished by having the binding element made of a shape memory material or by having at least part of the binding element made of a shape memory material.
According to an advantageous further feature of the binding element of the present invention, provision is made for the two side pieces to be biased toward each other at room temperature, whereby a clamping force is exerted on the sheets of the stack of documents inserted in the space between the side pieces; to open the binding element and to insert or remove sheets of the stack of documents, the binding element is heated to a temperature that is higher than room temperature and which has been preset in the shape memory material. When the preset temperature is reached, the binding element adopts a position in which the two side pieces are spread open relative to each other.
The binding element of the present invention can be constructed in very different ways. Thus according to a first variant, the entire binding element extending either over the full length of a side edge of the stack of documents or over only a certain sub-section is made of a shape memory material. This variant is relatively expensive, so an alternative solution provides only for parts of the binding element to be made of shape memory material. Either these parts are inserted in the material of the spine piece and/or the side pieces, or they are fastened to it and/or them.
This requires the spine piece, or at least the side pieces of the binding spine, to be made of a material whose elastic force is smaller than the elastic force of the shape memory material. Once this condition is fulfilled, the form of the binding element is determined by the preset form of the shape memory material which it adopts upon reaching a predetermined temperature.
An advantageous embodiment of the binding element of the present invention provides for the part or parts made of shape memory material to be a spring or a strip-shaped part or a wire. These parts, such as springs, are fastened in accordance with a first embodiment between the two side pieces above the spine piece of the binding spine; if provision is made for the spine piece to be in the center zones of the side pieces, it is possible for the spring to be fastened between the two side pieces underneath the spine piece.
Furthermore, the part or parts made of shape memory material can have essentially the form of the binding element with its spine piece and side pieces. They are then arranged either inside the binding spine or outside the binding spine. It is also possible, however, for them to be incorporated as an integral component of the binding spine.
In another advantageous feature, a further spine piece made of random material (cardboard, plastic, metal such as spring steel, etc.) and extending over the full length of the side edge of the stack of documents to be bound is fastened to the spine piece of the binding element or to the spine pieces of the individual parts of the binding element or binding spine.
A further advantageous aspect of the binding element of the present invention provides for the part or parts made of shape memory material to be an integral component of the spine piece and/or the side pieces of the binding spine, or for the part or parts to be fastened by suitable fastening means to the spine piece and/or the side parts of the binding spine.